(a) Field of the Invention
The present invention relates to a thermosetting resin composition which may be suitably used for the production of electrical laminates (insulating laminate, copper clad laminate for printed circuit board, etc.) having excellent flame resistance, electrical properties, and punching quality, and to an electrical laminate produced by using the thermosetting resin composition.
(b) Description of the Related Art
The recent progress of semiconductor technology and advancement of electronic apparatus have been increasing the demand for printed boards and, at the same time, the higher quality of printed circuits has been required. At the present time, in the production of electrical laminates, combination of a glass base material with an epoxy resin, combination of a paper base material with a phenolic resin or an unsaturated polyester resin, or the like are generally employed.
Particularly, in the production of paper base material-phenolic resin- or paper base material-unsaturated polyester resin-laminates and -printed circuit boards, which are used mainly for consumer appliances, improvement of flame resistance has been contrived for safety's sake and, in concurrence, improvement of size accuracy and decrease of punching temperature are also contrived for facilitating automatic mounting of parts by insertion.
The conventional flameploofing by introduction of halogen atoms in the resin skeleton and addition of various kinds of flame retardants has a disadvantage in that sufficient flame resistance cannot be attained without the decrease of the other necessary properties such as heat resistance, chemical resistance, electrical properties, etc.
Also, the conventional methods of improving punching quality by adding plasticizers or by endowing the resin skeleton with flexibility cause the decreases of heat resistance, chemical resistance, moisture resistance, etc.
In Japanese Patent Application Publication No. 60-17340 disclosed is a method wherein a resin obtained by reacting a halogenized bisphenol A diglycidyl ether with a dimer acid is used as the flame retardant for thermosetting resins, and in Japanese Patent Application Publication open No. 60-45061 disclosed is a method of using a resin varnish consisting of a dicyclopentadiene polyester resin, an acrylic ester of diglycidyl ether or glycidyl ester through a dibasic acid of 4 to 36 carbon atoms, and an organic peroxide. However, these conventional methods failed in providing laminates satisfying all requirements concurrently, that is, good flame resistance, improvement of the punching quality at low temperature, moisture resistance, chemical resistance, and excellent electrical properties.